Self-assembling organic semiconductors reported

Portland, Ore. - Israeli researchers have taken a page from nature's book to create self-assembling organic semiconductors. Unlike inorganic silicon semiconductors, organic materials are naturally self-assembling: All the complex development and growth experienced by living things evolved from the self-assembly of atomically precise organic materials. The researchers hope that within two years their semiconducting proteins, called "electronic peptides," could enable lighter, cheaper, lower-power, flexible electronics.

"Our aim is 100 percent control of electronic peptides," said professor Nir Tessler of the Faculty of Electrical Engineering at the Technion-Israel Institute of Technology (Haifa, Israel). "We want to prepare electronic peptides in the same precise way that electrical engineers at Intel or IBM prepare a silicon circuit."

By linking electronic peptides in protein chains, like conventional polymers, Tessler's group plans to produce various organic semiconductors that can both emit and detect light. Emitting electronic peptides are predicted to enable foldable, color organic-LED displays with a higher resolution than possible with inorganic methods. Likewise, the self-assembling methods for detectors could enable large-scale, flexible solar cells. Both displays and solar cells made from electronic peptides could be rolled up like a blanket. The researchers also predict that electronic peptides could enable new sensor devices that detect trace amounts of environmental toxins or, in the body, diseased cells before they can multiply.

"Eventually, we will run into engineering problems we will have to surmount, but so far our technique is working like magic," said Tessler.

Basic building blocksThe Technion research team's electronic peptides were synthesized following the same formula that nature uses to repair living cells-that is, building up molecules consisting of long protein chains by assembling them from amino acids, which are basic building blocks. An automatic peptide synthesizer straight out of a genetic-engineering lab was able to construct the precise combinations of amino acids necessary to create the team's semiconducting electronic peptides.

"We just choose the right building blocks to give us roughly the properties we are after, then choose the right sequence [for the blocks] and get exactly what we need," Tessler said. "There is no need to invent a new chemical process every time you want a different sequence."

While most organic materials quickly degrade when exposed to changes in humidity or temperature, the ultraprecise electronic-peptide material was found to be as durable as silicon devices. That durability prompted the researchers to obtain a patent and found Peptronics Ltd., a new Israeli company formed to commercialize the electronic-peptide patent. "Our precision manufacturing process creates electronic-grade material that retains its semiconducting properties better than other organic materials," said Tessler.

Currently, the researchers and the company are attempting to integrate the electronic-peptide material into the normal fabrication lines used to create silicon chips. Electronic peptides could be integrated onto silicon sensors as well.

Tessler's research team was supported by the Russell Berrie Institute for Research in Nanotechnology at Technion and the American Technion Society (New York), which claims to be the leading U.S. supporter of higher education in Israel.